One-Pot Synthesis of GeAs Ultrafine Particles from Coal Fly Ash by Vacuum Dynamic Flash Reduction and Inert Gas Condensation

Abstract

Ge-monopnictides (GeAs) plays critical role in high-tech industry, especially in the field of advanced optical devices and infrared. As a secondary material, coal fly ash could be further recycled to retrieve germanium and prepare GeAs material with high added values. Hence, the aim of this paper is to propose a one-pot synthesis that uses vacuum flash reduction and inert-gas consolidation method to prepare GeAs ultrafine particles. Germanium in coal fly ash can be successfully recycled; simultaneously, GeAs ultrafine particles were prepared. Separation principle and feasibility of this process was discussed. Temperature, carrier gas flow rate and system pressure were the major factors on formation, morphology and distribution of particle size of GeAs ultrafine particles. A three steps synthetic mechanism was clarified, namely, thermal rupture of coal fly ash and release of GeO2 and As2O3, the gas-solid phase reaction of GeO2, As2O3 and coke to generate metallic Ge and As in vacuum flash reduction. Meantime, GeAs were produced in the gas phase reaction. Finally, GeAs ultrafine particles were obtained by carrier gas condensation. In short, this research developed a practical and environment-friendly one-pot synthesis to recycle germanium in coal fly ash and prepare GeAs ultrafine particles with high added values.

Thermodynamics, Kinetics Model, and Reaction Mechanism of Low-Vacuum Phosphate Reduction Process for Germanium Recovery from Optical Fiber Scraps

“…Finally, under the conditions of high supersaturation, coagulation and coalescence of particles could occur between different metallic clusters. 43 With an increase in condensing distance, germanium oxide (GeO x ) particles are quenched, and collisions between particles slow down. The residence time of the condensed particles in the system decreases.…”

“…With this, the density of particles in the gas phase increase, resulting in higher collision frequencies between particles. Finally, under the conditions of high supersaturation, coagulation and coalescence of particles could occur between different metallic clusters . With an increase in condensing distance, germanium oxide (GeO x ) particles are quenched, and collisions between particles slow down.…”